Synonym

A synonym is a word or phrase that means exactly or nearly the same as another word or phrase in the same language. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greeksýn (σύν; "with") and ónoma (ὄνομα; "name"). An example of synonyms are the words begin, start, commence, and initiate. Words can be synonymous when meant in certain senses, even if they are not synonymous in all of their senses. For example, if one talks about a long time or an extended time, long and extended are synonymous within that context. Synonyms with exact interchangeability share a seme or denotational sememe, whereas those with inexactly similar meanings share a broader denotational or connotational sememe and thus overlap within a semantic field. Some academics call the former type cognitive synonyms to distinguish them from the latter type, which they call near-synonyms.[2]

In the figurative sense, two words are sometimes said to be synonymous if they have the same connotation:

...a widespread impression that ... Hollywood was synonymous with immorality...[3]

Metonymy can sometimes be a form of synonymy, as when, for example, the White House is used as a synonym of the administration in referring to the U.S. executive branch under a specific president. Thus a metonym is a type of synonym, and the word metonym is a hyponym of the word synonym.

Note that synonyms are defined with respect to certain senses of words; for instance, pupil as the aperture in the iris of the eye is not synonymous with student. Such like, he expired means the same as he died, yet my passport has expired cannot be replaced by my passport has died.

Some lexicographers claim that no synonyms have exactly the same meaning (in all contexts or social levels of language) because etymology, orthography, phonic qualities, ambiguous meanings, usage, etc. make them unique. Different words that are similar in meaning usually differ for a reason: feline is more formal than cat; long and extended are only synonyms in one usage and not in others (for example, a long arm is not the same as an extended arm). Synonyms are also a source of euphemisms.

The purpose of a thesaurus is to offer the user a listing of similar or related words; these are often, but not always, synonyms.

The word poecilonym is a rare synonym of the word synonym. It is not entered in most major dictionaries and is a curiosity or piece of trivia for being an autological word because of its meta quality as a synonym of synonym.